Membrane support

ABSTRACT

An apparatus for the separation of fluid mixtures having a plurality of three compartment subassemblies or units arranged in pairs, each subassembly consisting of a vapor, a heating, and a feed compartment defined from each other by separating barriers placed therebetween. The vapor compartment is placed common to a pair of subassemblies and contains therein a membrane barrier support structure, both sides of this structure placed in face to face contact with a semi-permeable membrane; said vapor compartment associated with fluid inlet and outlet side ports which communicate with fluid conduits serving a pair of identical compartments located in subassemblies that are positioned on opposite sides of the common vapor compartments.

United States Patent [151 3,695,444

Iaconelli 5] Oct. 3, 1972 [54] MEMBRANE SUPPORT 3,342,719 9/1967 Chen etal. ..204/30l Inventor: B- Iaconelli, Scituate, Mass. Greatorex ..2 1 X[73] Assignee: Ionics, Incorporated, Watertown, Primary Examiner-FrankA. Spear, Jr.

Mass. Attorney-Norman E. Saliba and Aaron Tushin '22 Filed: April 22,1970 [57] ABSTRACT [21] Appl' 3066l An apparatus for the separation offluid mixtures hav- Re'ated us. Applicafion Dam ing a plurality of threecompartment subassemblies or units arranged in pairs, each subassemblyconsisting of DlvlSlOIl 0f 1963, a vapor, a heating, and a feedcompartment defined Pat. No. 3,520,803. from each other by separatingbarriers placed therebetween. The vapor compartment is placed com- [52]US. Cl ..2l0/321, 210/541 mon to a pair of subassemblies and containstherein a [51] Int. Cl. ..B01d 31/00 membrane barrier support structure,both sides of this [58] Field of Search ..204/30l; 210/321, 541,486,structure placed in face to face contact with a semi- 210/433 459 490491 permeable membrane; said vapor compartment associated with fluidinlet and outlet side ports which [56] References Cited communicate withfluid conduits serving a pair of identical compartments located insubassemblies that UNITED STATES PATENTS are positioned on oppositesides of the common vapor art is. 2,249,063 7/1941 Swem ..2l0/486 comp2,778,096 l/1957 Weema ..2lO/54l X 4 Claims, 5 Drawing Figures E13SECOND COMMON HEATING SPACER E 44 SECOND COMMON 44 VACUUM SPACER D 6FIRST COMMON HEATING SPACER 54 i FIRST COMMON V VACUUM SPACER 43 beoPATENTED 01:13 1912 3,695,444

sum 1 n1 4 SECON D COM MON i l/ VACUUM SPACER 1 FIRST COMMON C e 42 62 5HEATING SPACER B13, 61 .M. FIRST COMMON 41 45 VACUUM SPACER INVENTOR 1WILLIAM B. IACONELLI PATENTEDIIBTB m2 3,695,444

SHEET 2 OF 4 SECOND COMMON i /HEATING SPACER SECON D COM MON VACUUMSPACER P keo 21 28 55 Fig: 2.

44 FIRST COMMON 43 W HEATING SPACER 45 L-ieo FIRST COMMON 5 VACUUMSPACER a V I\'\'1i.\"l'()R WILLIAM B. IACONELLI MEMBRANE SUPPORT Thisapplication is a division of Ser. No. 786,634 filed Dec. 24, 1968, nowUS. Pat. No. 3,520,803.

This invention relates to a fluid separation membrane apparatus andmethods of manifolding the various fluid streamswhich enter and/or leavethe chambers of the apparatus so as to prevent or reduce leakage of onestream into another. Specifically, it concerns the passing of two ormore streams of fluid into the appropriate chambers of a multichamberapparatus to prevent undesirable leakage of fluid in a manner whichminimizes the the pressure drop associated with manifold fluid flow andmaximizes the available active working surface area within theapparatus. It further relates to improved means for supporting themembranes during the fluid separation process to prevent rupturing ordeformation of said membranes. For purposes of this disclosure, 9. fluidis defined as a liquid, vapor, gas or a mixture of the same, and amembrane is defined as a barrier which is differentially permeable toone or more components of a fluid mixture.

Apparatus for carrying out membrane separation processes are frequentlyof the stack type such as that which is described in US. Pat. No.3,398,091 issued to J.L. Greatorex on Aug. 20, 1968. This patent is inthe hands of a common assignee, and the information therein isincorporated herein by reference. The spacers forming the compartmentsof the apparatus have the shape of open frames and are separated fromeach other by a membrane or other type of thin barrier. The introductionof fluids into and out of each thin compartment is difficult since thedistance between adjacent barriers is small and the fluid streamsentering the apparatus must be made to flow in generally parallel planeswithin the spacer compartments. The introduction and removal of fluid isby means of one or more conduits or manifolds which are generallyinternally formed within the stack by the alignment or registration ofholes or apertures in the gasketing area of the barriers and spacerframes forming the stack. Appropriate fluid inlet and/or outlet manifoldholes in each spacer are connected as desired to the fluid flow patharea of the compartment in that spacer by a connecting channel formed byremoving a section of the spacer frame material. These entrance and exitchannels may, for example, form narrow passageways connecting themanifold hole in the spacer with the fluidholding compartment area. Themanifold holes or apertures are located in an appropriate marginalgasketing area or may be in a more centrally located gasketing area. Thevarious fluids which may be circulated through the compartments arehydraulically separated from each other, each fluid being directed toand/or removed from the appropriate compartments by an independent setof inlet and outlet manifold holes.

The membranes or other barriers employed in a separation stack are thinand flexible so that under the application of small differentialpressures, bowing, deformation or deflection will occur. The membranearea which is highly susceptible to such deformation is adjacent to andencompassed within the fluid inlet and/or connecting channel area of thespacer. This critical membrane area will tend to deflect or deform intothe connecting channel under the pressure applied to gasket the elementsof the stack into a fluid-tight arrangement. Such deflection will alsooccur into a connecting channel when the fluid stream in thecompartment, which is on the same side of the membrane as the channel,is circulated under a lower pressure than that on the opposite side ofthe membrane. The result is that some of the liquid from one conduitstream will pass behind the membrane area which has deformed into theconnecting channel of another conduit stream, and thus enter the lowerpressured manifold as unwanted foreign material. Deformation isespecially serious in membrane processes in which a substantialdifferential pressure (5 or more p.s.i.) exists between the surfaces ofa membrane barrier. Past attempts to overcome the difficult problem ofdeformation and resulting conduit cross-leak have included an internalmanifold or conduit in a series flow arrangement employing one or morestream direction deflecting means as fully described in the heretoforementioned US. Pat. No. 3,398,091. Such fluid flow deflecting meansgenerally comprise two adjacently placed manifold holes located in thesame frame side of the gasketing area of a heating compartment spacerwith the holes connected to each other by a thin and narrow fluiddeflecting path cut out of the same spacer material. The flat heattransfer plate or sheet adjacent to one side of said heating compartmentdoes not contain holes which align with the two holes of the deflectingmeans and thus forms a flow barrier on that one side of the spacer. Thisarrangement allows a fluid stream to be received into one manifold holeof the stream deflecting means in a first perpendicular direction to thesurface of the transfer plate, pass along the thin connecting deflectingpath into the adjacent manifold hole and then flow away from this latterhole in a second perpendicular direction opposite to the firstdirection. However, because of the narrow deflecting flow path and thesharp turn required of the fluid stream entering and leaving thedeflecting means, the hydraulic pressure drop encountered within thesaid deflecting means is generally excessive and not desirable.

Therefore, it is an object of this invention to provide a novel membranestack separation apparatus having a flow arrangement for fluid streamswherein the manifold holes and connecting channels in the gasketing areaof the spacers are so placed and arranged to reduce the manifoldpressure drop in at least one of the fluid conduit streams by reducingthe fluid manifold distance within the apparatus and by further reducingthe number of sharp turns in the manifold path.

A further object is directed to systems for introducing and/or removingfluid streams to and from closely spaced compartments in a separationstack in a predetermined manner so as to eliminate the necessity ofspacers containing high pressure drop stream deflecting means.

A further object is to prevent membrane deformation and undesiredleakage of fluid from one compartment of a membrane separation apparatusinto another compartment.

A further object is to provide an improved type of membrane supportinggrid or structure whereby each membrane is adequately supported againstdeflection and possible rupturing without obstructing the removal ofvapor from the membrane surface.

A further object is to provide a single integral component whichfunctions as both a heat transfer sheet and a fluid feed compartment.

Various other objects and advantages will be particularly pointed outhereinafter in connection with the appended claims.

To better understand the invention, the description and drawings aremade with specific reference to a membrane permeation apparatus andprocess; however, it is not to be construed as limited thereto except asdefined in the claims. For a fuller understanding of the invention,reference should be made to the following detailed disclosures taken inconjunction with the drawings wherein like numerals are used todesignate like parts.

FIG. 1 is a perspective view of a section of a specific embodiment of amembrane permeation apparatus showing the arrangement of the structuralelements in exploded relationship with one another to illustrate fluidfeed internal within the apparatus through all the same typecompartments in series flow direction. In the embodiment shown, aheating spacer 12 is employed common between each repeating unit pair ofthe apparatus that is between unit B and C and between unit D and E.

FIG. 2 is also a perspective section of the apparatus showing analternate fluid flow arrangement for parallel feed to certaincompartments within the apparatus and wherein the means for passingfluids into and out of the apparatus are located on the side edges ofthe vacuum frame spacers 14 which spacers are preferably placed commonto a unit pair that is between unit A and B, between unit C and D, etc.

FIG. 3 is a perspective view partially in section showing a commonvacuum spacer frame in association with a preferred embodiment of amembrane supporting structure.

FIG. 4 is an enlarged detailed illustration of a preferred subsupportingforaminous element as is employed in the membrane supporting structureof FIG. 3.

FIG. 5 is a perspective view of a composite heat transfer-fluid feedcompartment spacer component which can be employed in the membraneseparation apparatus.

Briefly speaking, membrane permeation will allow the composition of aliquid mixture to be changed by allowing a portion of the mixture topermeate through an appropriate membrane which is more selective to thepassage of one or more components of the mixture relative to theremaining components. The components permeating the membrane are removedin the vapor phase. The composition of the permeate vapor recovered at agiven temperature and vapor pressure is determined by the composition ofthe feed mixture and by the nature of the membrane. A membrane which isstrongly hydrophilic will allow the selective permeation of water from amixture but will impede the evaporation of organic constituents. Thus,water can be removed from a coffee extract or from fruit and vegetablejuices without removal of any significant fraction of the volatileflavor or aroma constituents.

The permeation stack as illustrated in the drawings of FIGS. 1 and 2 isarranged similarly to a plate-andframe filter type press which may beoperated in a horizontal or vertical position and comprises a pluralityof basic units or subassemblies A through E placed between a pair ofterminal end plates (not shown). It is to be understood that any numberof basic units can be employed; the units arranged preferably in pairsin a repeated fashion between the end plates. A fluid-tight stack isobtained by applying the proper pressure against each end plate as bynuts and bolts (not shown) or other well known pressure means. When thestack is operated in a horizontal position a skeleton framework made upof two end supports connected by horizontal, parallel bars or rails maybe employed. On these bars a varying number of the frames or spacersforming the compartments of each subassembly can be supported andassembled into a fluid tight stack. The frames would be supported on therails by means of a pair of conventional supporting arms or handleslocated on opposite ends of the spacer frames. The elements of the stackcan be closed and tightened between the two end plates or heads by ascrew or hydraulic ram connected to the moveable head which forces thespacer frames together.

In the apparatus illustrated, each basic unit or subassembly comprisesthree individual compartments 7,8,9, separated from each other bybarriers 10 and 11 with some compartments located common between twounits. The heating compartments 7 are comprised of spacer members 12 andfluid feed compartment 8 are comprised from spacer members B13, C13,D13, E13, etc., and are separated from each other by a heat transfersheet 11 made, for example, of a thin sheet of suitable metal. Therequired latent heat of evaporation is supplied to the liquid in thefeed compartment 8 via the heat transfer sheet by circulating hot wateror steam through the heating compartment 7.

The vapor chamber 9 shown common between two subassemblies, that isbetween subassembly A and B and between subassembly C and D are formedfrom spacer frame member 14 and are separated from the adjacent feedcompartments 8 by a thin semi-permeable membrane 10. Spacer frame member14 is generally thicker than the other spacers and is convenientlyformed of a relatively rigid, chemically inert material such as plasticor stainless steel. Associated with certain sides of each membrane 10may be gasketing frame means (not shown) to allow the membrane andadjacent rigid spacer members to gasket with respect to one another.Associated with the vacuum spacer member 14 is support member 16 made offluidpermeable materials such as a porous metal, ceramic or plasticwhich is preferably held in the rigid frame of spacer 14 and made to fitinto the vapor or vacuum compartment 9. The support member is placed indirect face-to-face contact with the adjacent thin membranes to preventthe membranes from rupturing and bursting into the vapor compartment dueto the difference of pressure which will exist between the feed andvapor compartments during actual operation. A particularly suitableembodiment of a vacuum spacer member and its associated novel supportmember is described hereinafter in reference to FIG. 3.

Ideally, the vapor compartment is completely sealed off from theadjacent feed compartments to insure that any fluid entering the vaporcompartment will occur only by permeation through the separatingsemipermeable membrane barrier 10. However, such a condition is not easyto attain due to membrane bowing with the resulting cross leakage offluid from one compartment to another. Spacer members 12 and 13 haveetched or cut out central portions which preferably define a tortuousfluid-flow path area for the heating compartments 7 and feedcompartments 8. These compartments are confined by the frame of thespacer; said frame also functioning as a gasket with respect to theelements of the stack adjacent thereto. The flow path may alsoincorporate means (not shown) for promoting turbulent flow of fluidsalong the flow path area as fully disclosed in the U.S. Pat. Nos.2,708,658 issued May 17, 1955 in the name of N. W. Rosenberg and2,891,899 issued June 23, l959-in the name of E.A. Mason.

The membranes l0 employed for permeation are well known in the art. Eachmembrane is formed as a non-porous sheet or film made of an organicpolymer such as natural and synthetic rubbers, neoprene, polybutadieneor other polyolefins, polyvinyl chloride, copolymers ofvinylchloride-vinlidene acrylonitrile, polyvinyl butyral, celluloseesters such as cellulose acetate, cellulose propionate, cellulosebenzoate, cellulose nitrate, cellulose acetate-propionate, celluloseethers such as ethyl and methyl cellulose, ion-exchange membranes, etc.,to mention but a few of the many polymers that may be used. It is to beunderstood that the membrane material is chosen according to itspermeation characteristics inasmuch as polymers of the type describedexhibit different selectivities with respect to different liquids;hence, the choice depends on the nature of the mixture sought to beseparated. In order to obtain high permeability the membranes are quitethin preferably ranging in thickness, for instance, from 0.0001 0.01inches.

In the apparatus, particularly that illustrated in FIG. 1, each terminalpressure plate (not shown) may be provided with inlet and/or outletconnector tubes. To such tubes couplings can be made to carry fluid toand/or from the various compartments via the conduits 60, 61 and 62 ofthe stack in series flow by way of appropriate holes 40,4l,42,43,44, 45,and 46, and connecting channels 50,51,52,53,54,55 and 56 which areprovided in the gasketed areas of the various members of the stack.Vacuum pumps (not shown) or other means may be provided at certainconnector tubes to produce via conduit 61 the desired low pressurewithin the vapor compartments 9, or alternatively, a sweep gas may bepumped through the vapor compartments. Pumping means (not shown) arealso provided at appropriate inlet connecting tubes for the passage offluids respectively into feed compartments 8 and heating compartments 7and for the withdrawal of fluids from said compartment.

The elements of the stack are provided in their gasketing areas with oneor more holes or apertures 40 to 46 which are generally located in themargins of such elements. Certain holes in each spacer member areprovided with channels or slits 50 to 56 which connect with the openinterior of the spacers to allow a predetermined fluid stream to enterand/or leave the appropriate compartments, while other holes are provided without channels for by-passing other fluid stream to othercompartments. The particular arrangement of the holes and channels isdetermined in part by the location of the fluid inlet and outletconnecting tubes on the apparatus and also of-course on the particulardirection of fluid flow desired through the stack.

The drawing of FIG. 1 illustrates generally series flow internallythrough the stack of both the heat transfer stream through conduit 62and the feed stream through conduit 60, both streams being separate fromeach other. The streams may be operated concurrently orcounter-currently to each other as desired and are passed into one endof the stack and removed at the other opposite end. The passage of fluidstreams to the appropriate compartments and their withdrawal therefromis managed by the mainfold or conduit systems 60, 61 and 62 which runinternally through the stack in the general direction designated by thearrows. These conduits are formed by alignment of the appropriate holesor apertures located in the gasketed stack elements.

The elements of the stack are normally provided with at east one vacuummanifold hole 41 in addition to a plurality of other fluid mainfoldholes. The membranes 10 adjacent to each common vapor spacer 14 arenormally provided in their gasketed area with manifold holes similar innumber and location as the manifold holes in the said adjacent vaporspacer frame. The other elements of the'stack also contain vacuum holes41 similarly situated so that on assembly of the stack a vacuum conduit61 is formed internally through the cell by alignment of said vacuummanifold holes. The vapor compartments 9 formed by spacers 14 areconnected to their respective vacuum manifold holes 41 by means ofnarrow passageways or connecting channels 51. In operation, the fluidcomponent permeating the membrane will vaporize into the vaporcompartment and be removed therefrom through connecting channels 51 andfinally withdrawn from the apparatus via vacuum conduit 61 and collectedat the appropriate outlet connecting tube.

Each spacer located between a pair of heat transfer sheets or plates 11defines a heating compartment 7 common to a pair of units orsubassemblies. These heating spacers are provided with at least manifoldapertures 42 and 43 which are connected with the fluid flow path area ofthe heating compartment by connecting passageways 52 and 53respectively. Feed compartments 8 are similarly provided with at leastmanifold apertures 40,44 and 45 and the respective accompanyingconnecting channels 50,54 and 55 where required. The common heatingcompartment spacers l2 and heat transfer sheets 11 are also providedwith at least manifold apertures 40,44, and 45 which are aligned withsimilarly situated apertures 40,44 and 45 of feed compartment spacer 13.

It will be noted that the membranes (and also the vapor spacers) in nocase have manifold holes which are aligned with the influent andeffluent connecting channel manifold holes of the adjacent feed spacers13. By such an arrangement, the membrane area overlying the connectingchannel areas 50,54, 55 and 56 of the feed spacers will have a reducedtendency to bow into these connecting channels. Any bowing that mightoccur would in no event be harmful because due to the absence of amembrane manifold aperture in the area adjacent to the feed spacersconnecting channels and accompanying apertures 40,44,45 and 46, there isno possible way for the feed solution located in conduit 60 to flowunder the bowed area of the membrane into the vapor compartment.

It is preferable that two or more individual subassemblies be utilizedin pairs (A and B, C and D, etc.) betweenthe end pressure plates so thata vapor compartment 9 defined on both sides by membranes 10 will becommon to each subassembly of the pair. The vapor compartment 9 willthus serve to receive permeate from the two adjacent feed compartments 8as shown in the drawings. It is to be understood that additionalsubassemblies from that illustrated may be placed in a repeatingarrangement between the terminal pressure end plates.

The operation of the apparatus and the improved manner of directing thefluid streams through the stack may be more fully described by referringin particular to FIG. 1 which illustrates a manner of distributing astream 60 of a fluid feed mixture to each feed compartment 8 in amulti-unit stack by flowing said mixture internally through the stack inseries from one feed compartment to another feed compartment and so on.Another fluid stream 62 of, for example, hot water is simultaneouslypassed in a series manner into and out of each heating compartment 7. Athird stream 61, for example, a partial vacuum may be passed througheach of a third set of compartments for example, vapor compartments 9.All streams are normally kept separate from one another. There may undersome circumstances be a fourth and even a fifth stream. By the presentinvention, a feed stream ofa liquid mixture, for example, an aqueouscoffee extract having 25 percent solids, is passed by pumping means intothe terminal plate inlet feed tube at a rate of about one gallon perhour and flows through conduit 60 as shown by the direction of thebroken line arrows. The stack employed is comprised of three repeatingunit pairs, (subassemblies A through F) with a total utilized membranepermeation area of about 40 ft*-. The feed mixture stream 60 afterby-passing the feed compartment B8, of subassembly B and on enteringinlet manifold aperture 45 of feed compartment C8 of subassembly C iscaused to flow in a tortuous path across the said latter feedcompartment to outlet manifold aperture 40. Since the adjacent membrane10 of, for example, cellulose nitrate, does not have an aperture whichaligns with outlet manifold aperture 40, the solution leaving this feedcompartment is forced to flow back to the feed spacer 813, ofsubassembly B and into inlet aperture 40 Since the membrane 10 adjacentto the feed spacer of subassembly B also does not contain an aperturewhich aligns with manifold inlet aperture 40, the feed solution mustflow across the feed compartment B8 to outlet manifold aperture 44 whereit is then forced to flow once again in a direction towards the feedspacer C13 of subassembly C through manifold apertures 44 via conduitmeans 60. This stream 60 travels in a direction past subassemblies C andD until it enters manifold inlet hole 44 of the feed spacer E13 locatedin subassembly E. The stream then follows the same general path as waspreviously described with reference to subassemblies B and C, that is,it flows across and out of the feed compartment E8 of subassembly E,then back to the feed compartment D8 of subassembly D where it is thenwithdrawn at effluent aperture 45 and directed to the next adjacentlyplaced subassembly (not shown). Eventually after passing in series flowthrough all the remaining feed compartments in the manner described,

it is finally withdrawn from the apparatus at an appropriate outlettube. It is collected as a 52 percent concentrated product at a rate ofabout 0.5 gallons per hour. The feed mixture solution can first beheated before entering the stack; preferably to a temperature of aboutF. and its temperature maintained during its series passage through thestack by absorption of heat from the adjacent heating compartments 7.Heat transfer fluid, for example, water at a temperature of about F. iscontinuously pumped into an inlet tube associated with the end pressureplate at about two gallons per minute and allowed to flow in seriesthrough each heating compartment of the stack via conduit system 62. Inthe passage of such fluid through the heating compartments the heatcontained therein will be transferred to the feed mixture contained inthe feed compartments by means of the separating heat transfer sheets orplates. On passage out of the stack the heat transfer fluid may bereheated and recirculated back to the stack.

The pressure in the vapor compartment 9 is maintained at a lowerpressure than that in the feed compartment, for example, by a partialvacuum in the compartment by evacuation at the appropriate tube outletsusing a vacuum pump or other suitable device. Water from the feedmixture solution (for example, a coffee extract) contained in feedcompartment 8 will preferentially permeate the water permeable membranel0 emerge from the lower pressure side of the membrane as a vapor whereit is quickly removed via connecting channel 51. The vapor is withdrawnfrom the stack at outlet tubes associated with the pressure end platesand then condensed and finally collected at a rate of about 5 pounds perhour.

It should be noted particularly in FIG. 1 that the fluid feed mixturestream 60 in its passage through the feed compartment of a subassemblypair (such as subassemblies B and C) initially by-passes the firstlocated subassembly or unit B prior to passing into and through the feedcompartment C8 of the adjacently located second subassembly or unit C.The stream 60 then returns to the first unit B where it passes into andout of the units feed compartment B8, and then subsequently flows in itsinitial direction towards the next adjacently located unit pair D and E.It is readily seen that the feed stream 60 in its passage through thefeed compartments of a subassembly pair (B and C) as above describedrequires four sharp 90 turns. In the prior art apparatus employingstream deflecting means as described in the aforementioned U.S. Pat. No.3,398,091 there is required eight sharp 90 turns in the fluid streamdirection to accomplish passage through the feed compartments of asubassembly pair. This excessive number of turns is due to the presenceof two sets of stream deflecting means associated with the gasketingarea of the heating spacers and incorporated within the feed streammanifold conduit path 60. The objective of this present invention ofreducing the manifold hydraulic pressure drop is therefore readilyaccomplished by the elimination of those high pressure drop deflectingmeans employed in the prior art apparatus.

FIG. 2 illustrates the embodiment directed to an arrangement in whichsimilar compartments located in separate subassemblies are fed inparallel flow from a single fluid stream that initially splits into afirst and second feed stream. The fluid preferably do not enter andleave the apparatus through pressure plates located at the terminal endsof the apparatus as was described hereinabove with respect to FIG. 1,but instead generally by means of fluid connecting tubes or portslocated on two or more side edges of the rigid vacuum spacer framemembers. The first stream will pass in one direction to a certainsubassembly and the second stream in another direction to an oppositelylocated subassembly. The streams after passing in parallel flow throughsimilar compartments of the respective subassemblies will flow towardseach other and combine once again into a single stream. Of-course theunits or subassemblies are still arranged preferably in pairs betweenend plates having the necessary pressure means to obtain a fluid tightstack assembly. If desired it is permissible for some of the connectingtubes to be in association with the end plates and others with the sideof the vacuum spacer frames.

In the apparatus illustrated the vacuum spacer frame shown common to apair of units or subassemblies is provided with a set of inlet andoutlet connecting tubes, 20,21,22,23, and 24 extending into oppositelylocated side edges of the spacer frame. Through these tubes fluid can bemade to pass and be withdrawn from the appropriate compartments throughinternal conduits means formed by sets of aligned manifold holes. Eachvacuum spacer frame 14 however does not necessarily carry the samenumber of tubes nor are their locations similar to their neighboringvacuum spacer. For example only every alternate vacuum spacer need beproand heat transfer stream 30 attention is directed especially to thesecond common vacuum spacer located between subassemblies C and D. Asshown therein the feed solution 31 designated by the broken line arrowis passed by a pump 27 into inlet tube which is connected to feedconduit 60 formed by means of aligned manifold holes 44. The feed streamwill divide into two half streams each initially going in completelyopposite directions via conduit 60 formed by the appropriately locatedmanifold holes. The first of said half stream will by-pass feedcompartment C8 located in subassembly C, enter and leave feedcompartment B8 locatedin subassembly B and then by means of manifoldholes 40 flow back to the said second common vacuum spacer with itsassociated manifold hole 40 and outlet tube 23. The said second halfstream follows the same general flow pattern as above described wherebyit by-passes feed compartment D8 of subassembly D, enters and leavesfeed compartment E8 of subassembly E and returns back to the secondcommon vacuum spacer where it combines within manifold 40 with the saidentering first half stream. The combined streams are thereafterwithdrawn from the apparatus and collected at outlet tube 23. Both halfstreams flow in a direction which are mirror images to each other. Ineach case the feed compartments C13 and D13 located in the subassemblypair (CD) that is associated with the second common vacuum spacer arenot serviced by the feed stream 31 entering said second common vacuumspacer. Feed compartment C13 will be serviced through conduit 60 formedfrom manifold holes 45 from the feed stream 31 which entersthe firstcommon vacuum spacer associated with a subassembly pair A, B. Similarlyfeed compartment D13 will be serviced by the feed stream originatingfrom the third common vacuum spacer associated with subassembly pairE,F. (not shown) In a similar manner the heat transfer stream 30 ispassed by a pump 28 into inlet tube 21 which is connected to the conduitformed by aligned manifold holes 43. This stream also splits into twostreams with each stream initially flowing away from each other incompletely opposite directions. The first of said streams will pass intothe heating compartment 7 located in subassembly D and the second streamwill pass into the heating compartment located in subassembly C. Bothstreams on passing out of their respective heating compartments willflow through the conduit 60 formed by manifold holes 42 in a directiontowards each other back to the common vacuum spacer from which theyoriginated. The streams meet and combine within the manifold hole 42associated with the effluent tube 24 located on said vacuum spacer.frame and thereafter this stream is removed from' the apparatus andcollected as desired. In this case it will be noted that the heatingstream 30 entering the second common vacuum spacer will service theheating compartments located in those subassemblies which are adjacentto and separated by said second common vacuum spacer.

The desired lower pressure in the vacuum compartments 9 is obtained byevacuation at outlets 22 by a vacuum pump 26 or other suitable means.The number of said vapor outlets 22 employed throughout the stack mayvary as desired but it is preferred that at least one outlet be locatedon a side of each vacuum spacer frame. Since each vacuum compartment9 isserviced by its own separate vapor outlet 22, it is not necessary thattheir be manifold holes 41 forming an internal conduit 61 connecting allthe vacuum compartments as shown in FIG. 2. In fact is is generallypreferred that there be no manifolding between the vacuum spacers. Bysuch as arrangement each vacuum compartment may be controlled directlyand independently of the others to allow if so desired variations in thedegree of evacuation employed therein. The number of subassembliesarranged between the end plates of a stack and the available membranearea employed can varyto a wide degree depending on the production ratedesired. In the apparatus of FIG. 2 the effluent streams collected fromthe effluent tubes of one vacuum spacer frame member can serve as theinfiuent stream to the next adjacently located vacuum frame member andflow continuously in a series arrangement into and out of a plurality ofsuch frames.

FIG. 3 illustrates a common vacuum spacer with associated means forsupportingthe membrane since the membranes employed have littlestructural rigidity by themselves. The problem is one of supplyingsufficient totalmember support without undully obstructing the removalof vapor permeate from the membranes. In the form shown the commonvacuum spacer member 14 for use particularly in the apparatus of FIG. 2is provided with a solid, non-porous frame or rim 80 about the spacersexternal periphery. The frame contains at least one vapor tube 22 andconnecting channel 51 communicating with the vapor compartment 9 andalso manifold holes 42,43,44, and their associated tubes 24, 21, 20. Themanifold holes do not communicate with the interior of the vaporcompartment but merely go through the thickness of the frame. Otherholes and tubes althrough not shown may be required. Because eachmembrane is placed directly against its respective supporting means 16,the membrane surface through which transfer takes place is restricted tothe area which is exposed and not obstructed by the direct contact withthe supporting means. In order to greatly increase the surface area ofeach membrane available for exposure to permeation, the invention in apreferred form comprises a thin spread sheet 81 of a highly porous orfine mesh material for example a fine mesh or woven screen of metal,plastic or other material placed in direct contact with the membranesurface. The fine screen is countersunk within the vacuum frame andpresents a flat surface with the gasketing edge of the frame. A meshsize between 25 to 80 (US. Sieve Series) has been found satisfactory,the preferred mesh size range being between 45 to 55. Each fine meshscreen material is supported and in direct contact with an associatedback-up screen 82 of much larger mesh or pore size. This back-up screengenerally possesses a mesh or pore size three to six times larger thanthe finer screen; the preferred mesh size being between 5 to 10. Thusthe vapor or vacuum compartment 9 enveloped within the spacer frame 80is confined on both sides by the combination of a fine and coarse meshor pore material. To give structural support to each pair of screens orporous sheets it was found advantageous to employ highly perforatedsubsupport means 82 placed between the two sets of screen pairssubstantially filing the vapor compartment. The subsupport means 83should be provided with a multiplicity of large channels or pores toprovide passageways for vapor movement as unimpeded as possible butstill provide complete support for the pairs of screen. Thesubsupporting element although possessing a highly foraminous orexpanded structure should have a plurality of supporting points 85 indirect contact with each juxtapoised coarse mesh back-up screen. Thesubsupport may have a pyramidal or corrugated design. A particularlyexcellent subsupporting structure is one known as SUPER- TUBULUS havingsubstantially oval type tubular openings 84 as shown in detail by FIG.4. Structures having such a SUPER-TUBULUS design are availablecommercially from Krieg and Zivy Industries, Paris, France. The typeemployed in the present invention and found satisfactory was constructedof 316 stainless steel with the long axis of the tubular openingmeasuring about three-fourths inch and the short axis aboutthree-sixteenths inch. SUPER-TUBULUS as well as commercially availableexpanded metal mesh is the preferred material for use as the foraminoussubsupporting structure. Both materials are made by cutting rows of aseries of fine slits in a sheet of the desired material. To form theexpanded mesh material the sheet is pulled perpendicular to the longaxis of the slits resulting in the expansion of the slits to formessentially expanded diamond shaped holes. In the case of theSUPER-TUBULUS supporting structure it appears that two opposite ends ofthe sheet are pushed together parallel to the direction of the slitsforcing the metal defined within the area of two adjacent slits tobuldge and push away as a metal strip in a direction perpendicular tothe face of the sheet. The forcing is controlled to allow everyalternate metal strip in each row to buldge out in one direction and theremaining strips in the row in a diametrically opposite direction toform the tubular openings 84 and associated support points 85.

In FIGS. 1 and 2 the heat transfer sheet 11 is shown as a separateentity from that of its adjacent fluid feed compartment 8. However, thepreferred embodiment is to fabricate these two elements into a singleintegral structure comprising a composite heat transfer platefluid feedcompartment. FIG. 5 shows a perspective view of a preferred type of thecomposite element constructed for example of a 0.080 inch thick, flat,stiff and durable plate of thermally conductive material such asstainless steel and the like. On one face of the sheet is a tortuousfluid flow path 91 which has been chemically milled or etched into thesurface of the plate for a depth of about 0.020 inch. This singlecontinuous flow path is defined by walls 92 terminating in edges withthe axis of the path preferably running parallel to the face of theplate. The depth and length of the etched or recessed area 91 may varywithin wide limits but is preferably kept to a minimum thicknessprovided the hydraulic pressure drop resulting therefrom is acceptableunder the contemplated use. The series of integral prejections forminglong ribs 93 will direct a liquid between manifold holes 42 and 43 toflow in a continuous channel. In practice many more integral ribs may beused than that illustrated and the recessed flow path area may havedesigns other than that specifically shown. In close proximity to theinlet and outlet manifold holes there may be located a series ofintegral projections or short ribs 96 which may vary in number andshape. On assembly of the stack the adjacent membrane will contact andgasket against the flat surfaces of the peripheral frame area 94 andthat of the projecting long and short ribs. For this reason thegasketing area should be smoothly coated with a chemically and heatresistant, slightly pliable plastic to assist in forming a leak proofseal with the adjacent membrane. Preferably the entire side of thecomposite heat transfer-fluid feed compartment 90 containing the flowpath 91 should have its surface completely coated with at least a 1 milcoating of a commercially available plastic material. The fluorocarbonelastomers are the preferred coating material and include for example,tetrafluoroethylene, (TEFLON chlorotrifluoroethylene (KEL-F),fluorinated ethylenepropylene (FEP), polyvinylidene fluoride (PVF) andthe like. This will provide an exceptionally smooth and nonstick surfacein the flow path area so as to reduce the tendency for the adhesion anddeposition of solids from the fluid mixture traversing the flow pathareas especially where the fluid mixture comprises liquid food solutionssuch as coffee extract, whey etc. TEFLON is a particularly good coatingmaterial since it will lessen the possibility of the membranes stickingstrongly against the gasketing areas so that on disassembly of the stackthe membranes can be removed without tearing or otherwise damaging thesame.

The reverse face of the composite plate (not shown) functions as theheat transfer area and as such may remain as a flat surface. On assemblyof the stack, this flatheat exchanger surface will contact and lieagainst the adjacent heating spacer 12. The composite plate 90 is alsoprovided with a plurality of the mainfold holes 40,41, 44, 45 and 46located in the peripheral gasketing frame area to allow fluids to bypassthe said feed compartment on their passage to or from other compartmentsof the subassembly stack. A pair of arms 95 may be used to facilitatehandling and for support of the plate.

The number of subassemblies employed between the end plates of a stackand the membrane area available for transport can of course varydepending on the volume of feed required to be processed. A plurality ofconsecutively arranged permeation stacks may be used to effect a highdegree of concentration or separation, in which case the effluentmixture from one stack may serve as the influent feed mixture to thenext stack, and so on. The permeation apparatus may be employed in acontinuous operation or may be applicable to batch type or feed andbleed systems.

The description of the invention and the drawings have been made withspecific reference to a membrane permeation (pervaporation) apparatusand process; however, the invention is not to be construed as limitedthereto except as defined in the appended claims and is, in particular,useful also in mass diffusion, gaseous diffusion (molecular effusion)dialysis, electrbdialysis, piezodialysis, thermodialysis, osmosis,electroosmosis, piezoomosis (reversed osmosis) theremoosmosis,ultrafiltration (hyperfiltration), electrodecantation and other membraneseparation processes.

The embodiment of the invention in which an exclusive property orprivilage is claimed are defined as follows:

1. A membrane support spacer comprising a frame section defining acompartment substantially filled with a porous support member nestingwithin the frame of said spacer, said frame section containing aperturemeans, the said porous support member having on both major faces finelyporous sheet means presenting a substantially flat surface flush withthe surface of said frame, each side of said finely porous sheet meansfacing the interior of the said compartment being in contact with a morecoarsely porous back-up sheet support means, said coarse sheet meansfurther supported with highly foraminous subsupport means disposedbetween said back-up sheet means and substantially bridging the spacetherebetween, said subsupport means having a plurality of supportingpoints contacting each of said coarsely porous sheet means, the saidsubsupport means comprising a metal sheet having rows of slits cuttherein, the strip of metal defined within the'area of two adjacentslits extending or bulging outwardly in a direction perpendicular to thesurface of said metal sheet with the top or most extended portion ofsaid bulge forming the said supporting points, the alternate metalstrips in each row bulging or extending outwardly in one direction withthe remaining metal strips of the said row extending outwardly in anopposite direction, forming a substantially tubular shaped opening forproviding passageways for unimpeded vapor movement therethrough.

2. The frame section of claim 1 characterized in that at least some ofsaid aperture means contained therein are in communication with portmeans extending outwardly to an exterior side edge of said frame toprovide inlets and outlets for the flow of fluids into and out of saidapertures.

3. A membrane support spacer comprising a frame section defining acompartment substantially filled with a porous support member nestingwithin the frame of said spacer, said frame section containing aperturemeans, the said porous support member having on both major faces a 30 tofine mesh size screen presenting a substantially flat surface flush withthe surface of said frame, each side of said fine screen facing theinterior of the said compartment being in contact with coarse screenmaterial having a mesh size three to six times larger than said finescreen, said coarse screen being supported with highly foraminoussubsupport means disposed between said coarse screens and substantiallybridging the space therebetween, said subsupport means having aplurality of supporting points contacting each of said coarse meshscreen, the said subsupport means comprising a metal sheet having rowsof slits cut therein, the strip of metal defined within the area of twoadjacent slits extending or bulging outwardly in a directionperpendicular to the surface of said metal sheet with the top or mostextended position of said bulge forming the said supporting points, thealternate metal strips in each row bulging or extending outwardly in onedirection with the remaining metal strips of the said row extendingoutwardly in an opposite direction, forming a substantially tubularshaped opening for providing passageways for unimpeded vapor movementtherethrough.

4. A membrane support spacer comprising a frame section defining acompartment substantially filled with a porous support member nestingwithin the frame of said spacer, said frame section containing aperturemeans, the said porous support member having on both major faces a finescreen of about a 50 mesh size presenting a substantially flat surfaceflush with the surface of said frame, each side of said fine screenfacing the interior of the said compartment being in contact with coarsescreen material having a mesh size of about 10, saiD coarse screen beingsupported with highly foraminous subsupport means disposed between saidcoarse screens and substantially bridging the space therebetween, saidsubsupport means having a plurality of supporting points contacting eachof said coarse mesh screen, the said subsupport means comprising a metalsheet having rows of slits cut therein, the strip of metal definedwithin the area of two adjacent slits extending or bulging outwardly ina direction perpendicular to the surface of said metal sheet with thetop or most extended portion of said bulge forming the said supportingpoints, the alternate metal strips in each row bulging or extendingoutwardly in one direction with the remaining metal strips of the saidrow extending outwardly in a diametrically opposite direction, form-

1. A membrane support spacer comprising a frame section defining acompartment substantially filled with a porous support member nestingwithin the frame of said spacer, said frame section containing aperturemeans, the said porous support member having on both major faces finelyporous sheet means presenting a substantially flat surface flush withthe surface of said frame, each side of said finely porous sheet meansfacing the interior of the said compartment being in contact with a morecoarsely porous back-up sheet support means, said coarse sheet meansfurther supported with highly foraminous subsupport means disposedbetween said back-up sheet means and substantially bridging the spacetherebetween, said subsupport means having a plurality of supportingpoints contacting each of said coarsely porous sheet means, the saidsubsupport means comprising a metal sheet having rows of slits cuttherein, the strip of metal defined within the area of two adjacentslits extending or bulging outwardly in a direction perpendicular to thesurface of said metal sheet with the top or most extended portion ofsaid bulge forming the said supporting points, the alternate metalstrips in each row bulging or extending outwardly in one direction withthe remaining metal strips of the said row extending outwardly in anopposite direction, forming a substantially tubular shaped opening forproviding passageways for unimpeded vapor movement therethrough.
 2. Theframe section of claim 1 characterized in that at least some of saidaperture means contained therein are in communication with port meansextending outwardly to an exterior side edge of said frame to provideinlets and outlets for the flow of fluids into and out of saidapertures.
 3. A membrane support spacer comprising a frame sectiondefining a compartment substantially filled with a porous support membernesting within the frame of said spacer, said frame section containingaperture means, the said porous support member having on both majorfaces a 30 to 80 fine mesh size screen presenting a substantially flatsurface flush with the surface of said frame, each side of said finescreen facing the interior of the said compartment being in contact withcoarse screen material having a mesh size three to six times larger thansaid fine screen, said coarse screen being supported with highlyforaminous subsupport means disposed between said coarse screens andsubstantially bridging the space therebetween, said subsupport meanshaving a plurality of supporting points contacting each of said coarsemesh screen, the said subsupport means comprising a metal sheet havingrows of slits cut therein, the strip of metal defined within the area oftwo adjacent slits extending or bulging outwardly in a directionperpendicular to the surface of said metal sheet with the top or mostextended position of said bulge forming the said supporting points, thealternate metal strips in each row bulging or extending outwardly in onedirection with the remaining metal strips of the said row extendingoutwardly in an opposite direction, forming a substantially tubularshaped opening for providing passageways for unimpeded vapor movementtherethrough.
 4. A membrane support spacer comprising a frame sectiondefining a compartment substantially filled with a porous support membernesting within the frame of said spacer, said frame section containingaperture means, the said porous support member having on both majorfaces a fine screen of about a 50 mesh size presenting a substantiallyflat surface flush with the surface of said frame, each side of saidfine screen facing the interior of the said compartment being in contactwith coarse screen material having a mesh size of about 10, saiD coarsescreen being supported with highly foraminous subsupport means disposedbetWeen said coarse screens and substantially bridging the spacetherebetween, said subsupport means having a plurality of supportingpoints contacting each of said coarse mesh screen, the said subsupportmeans comprising a metal sheet having rows of slits cut therein, thestrip of metal defined within the area of two adjacent slits extendingor bulging outwardly in a direction perpendicular to the surface of saidmetal sheet with the top or most extended portion of said bulge formingthe said supporting points, the alternate metal strips in each rowbulging or extending outwardly in one direction with the remaining metalstrips of the said row extending outwardly in a diametrically oppositedirection, forming a substantially oval shaped opening for providingpassageways for unimpeded vapor movement therethrough, the long axis ofthe opening measuring about three-fourths inch and the short axis aboutthree-sixteenths inch.